1. Field of the Invention
The present invention relates to a pattern forming apparatus and a pattern forming method used in, for example, manufacturing a flat panel display, wiring board, IC tag and the like.
2. Description of the Related Art
Conventionally, photolithography plays a main role in forming a fine pattern on a base material surface. However, while this photolithography asks higher resolution or greater performance, it needs huge and highly-expensive manufacturing equipment and its manufacturing cost becomes higher according to the resolution.
Meanwhile, in the field of manufacturing a semiconductor device, an image display and the like, there are increasing demands for performance improvement and lower costs, and it is difficult for the above-mentioned photolithography to meet these needs. In such a situation, attention is being paid to a pattern forming technique using digital printing technique.
On the other hand, for example, the inkjet technique is being brought into practical use as a patterning technique taking advantage of a simple apparatus and non-contact patterning. However, there are limits in increasing the resolution and productivity. In other words, in this point, the electrophotographic system, or particularly, the electrophotographic system using liquid toner, has excellent potential.
For example, there is proposed a method of using electrophotographic system to form a color filter, black matrix, phosphor layer for a flat panel display front board and the like (see, for example, Jpn. Pat. Appln. KOKAI Publication Nos. 2004-30980 and 6-265712).
However, in the field of flat panel displays, there is an increasing demand for higher resolution and formation of a pattern of higher resolution with higher positional accuracy. However, this need cannot be satisfied by the above-mentioned electrophotographic system. This is because the resolution of the writing optical system is about 1200 dpi at most, which is not enough to assure higher resolution and higher positional accuracy. In addition, there is a problem that the wide wiring optical system for recent larger-sized displays cannot yet be realized.
On the other hand, there has been proposed a method for forming a pattern of phosphor or the like on a display front glass by using an electrostatic printing plate having patterns of different electrical resistance on the surface in place of photoreceptor, making liquid toner act on this plate to develop a pattern and transcribe this pattern image onto a glass plate (see, for example, Jpn. Pat. Appln. KOKAI Publication No. 2002-527783).
However, after the inventors of the present application carried out experiments and studied intensively, they found the following substantial problems of this method.
First, the developed image with use of liquid toner often has a film thickness of 1 μm or less, and is not suitable for thick film formation such as phosphor layer and color filter of a display. Hence, there needs to be further new ideas if the liquid toner is used to realize highly-accurate thick film forming.
In addition, when a corona charger is used to transfer the developed image onto the glass plate, corona charge propagates on the glass surface and is leaked, which tends to cause unstable transfer performance. In addition, a space charge tends to be stored inside the glass and it is difficult to form a transfer electric field that is stronger than this space charge in the corona transfer. Further, this problem is exacerbated after a first color developed image is transferred, which makes it more difficult to transfer the second and third color developed images onto the glass plate.
Further, in the method of using an electrostatic printing plate, it is difficult to develop image of plural colors at the same time, which makes it necessary to perform development and transferring process for each color. This presents problems of longer processing time for one-time print and lower operation rate.